Exposure to Air Pollution Found to Up Transient Risk of MI

Short-term exposure to air pollutants ups risk of myocardial infarction one to six hours later

WEDNESDAY, Sept. 21 (HealthDay News) -- Short-term exposure to particles with a diameter <10 µm (PM10) and nitrogen dioxide (NO2) in the air is associated with a short-term increased risk of myocardial infarction (MI) one to six hours later, according to a study published online Sept. 20 in BMJ.

Krishnan Bhaskaran, Ph.D., from the London School of Hygiene and Tropical Medicine, and colleagues investigated the association (at an hourly temporal resolution) between exposure to air pollutants (PM10, ozone, carbon monoxide, NO2, and sulfur dioxide) and MI with short time lags of one to six, seven to 12, 13 to 18, 19 to 24, and 25 to 72 hours in single and multi-pollutant models, after adjusting for ambient temperature, relative humidity, circulating levels of influenza and respiratory syncytial virus, day of the week, holidays, and residual seasonality within calendar months. A total of 79,288 patients with MI from England and Wales were evaluated between 2003 and 2006 to measure the risk of MI per 10 µg/m³ increase in pollutant levels.

The investigators identified a short-term increase in MI risk one to six hours after PM10 and NO2 exposure from single and multi-pollutant models, with a weak independent PM10 effect seen in the multi-pollutant model (P = 0.05). Following the immediate increase in risk, reductions were seen at longer time lags. In the 72 hour period after exposure, no net excess risk was seen to be associated with the five pollutants studied.

"Both single and multi-pollutant models suggested that higher ambient levels of PM10 and NO2 were associated with short-term increases in MI risk one to six hours later," the authors write.